Diversity of Fusarium Species and Their Mycotoxins in Cereal Crops from the Asian Territory of Russia.

Up-to-date information on the occurrence of Fusarium fungi and their mycotoxins in the grain of wheat, barley and oats grown in the Urals and West Siberia in 2018‒2019 is presented. Mycological analysis of grain revealed at least 16 species of Fusarium fungi. The F. sporotrichioides, F. avenaceum, F. poae, and F. anguioides were predominant, and the proportions of these species among all Fusarium fungi found in the grain were 31, 20, 19, and 13%, respectively. Fusarium graminearum and its mycotoxin deoxynivalenol (DON) are often occurred in grain mycobiota of cereal crops on the territory of both the Urals and West Siberia. New records of fungal species that are rare in the Asian territory of Russia were detected: F. langsethiae and F. sibiricum, which are mainly producers of type A trichothecene mycotoxins, were found in the Kurgan and Kemerovo regions, respectively. In addition, F. globosum that is able to produce fumonisins was detected in Altai Krai and Omsk region. The diversity of Fusarium species was higher in wheat and barley grain samples than in oats. The HPLC-MS/MS method was used to analyse the content of 19 mycotoxins produced by Fusarium fungi. The highest diversity of mycotoxins was found in wheat grain (maximum 12), compared with oats (9) and barley (8). The T-2 and HT-2 toxins, DON, nivalenol, moniliformin (MON) and beauvericin (BEA) occurred more often in the grain samples, compared with other mycotoxins, but their amounts varied significantly, depending on the weather conditions in sampling year and the plant species. The average content of DON (maximum amount was 375 µg/kg) in wheat grain was 5 times higher than its average content in barley grain, and this mycotoxin was not detected in oat grain. The contamination with T-2 and HT-toxins (maximum amounts were 2652 µg/kg and 481 µg/kg, respectively), as well as with BEA (maximum amount was 49 µg/kg) was typical for barley and oat grain samples. The content of MON (maximum amount was 50 µg/kg) in the grain of three different small grain cereals was similar.

Identification and Toxicological Characterization of Alternaria japonica Strains.

Fungi of the genus Alternaria are producers of biologically active compounds. Alternaria japonica is pathogenic to small radish and certain other crucifers, but has not been studied in sufficient detail. Discrepant data on its toxic metabolites are available in the literature, possibly because a limited set of nutritive substrates was used in culturing or species identification of the strains was incorrect. The objectives of this study were to accurately identify the Russian A. japonica strains and to assess the A. japonica toxigenic potential. Four Russian A. japonica strains were identified using a multifaceted approach, which included analyses of morphological characters (the diameter and morphology of colonies grown on the diagnostic media potato carrot agar (PCA) and yeast extract-glucose (YES) agar for one week), the conidial size, and the presence of chlamydospores), the nucleotide sequences of DNA markers (ITS and EF1α regions), and chemotaxonomic data (mycotoxin production). Biomass and extractive substance yields of A. japonica cultures were found to significantly depend on the composition of the liquid medium. Minor differences between the A. japonica strains were detected via metabolite profiling by HPLC/MS-UV. Extracts of A. japonica cultures exerted phytotoxic activity toward small radish leaves and cytotoxicity toward Paramecium caudatum to a level comparable with that of A. tenuissima extracts. Brassicicolin A, dihydrobrassicicolin A, and phomenins A and B, which are known for several species of the genus Alternaria, were identified in A. japonica extracts. Mycotoxins (alternariol, its methyl ether, tentoxin, tenuazonic acid, and altenuene), which are characteristic of the cosmopolitan species A. tenuissima, were not detected in cultures of the A. japonica strains. Extract toxicity and the yield of extractive substances were studied in the A. japonica strains, and strain MFP244011 proved promising as a producer of known and, presumably, new toxins upon culture on the M1D synthetic medium or semisynthetic liquid media (e.g., the Sabouraud medium).

Resistance of oat breeding lines to grain contamination with Fusarium langsethiae and T-2/HT-2 toxins.

Fusarium disease of oats reduces yield quality due to decreasing germination that is caused by the contamination of grain with mycotoxins produced by Fusarium fungi. The aim of this study was to characterize the resistance of naked breeding lines of oats to fungal grain infection and to contamination with T-2 and HT-2 toxins. Thirteen naked oat breeding lines and two naked varieties, Nemchinovsky 61 and Vyatskiy, as well as a husked variety Yakov, were grown under natural conditions in the Nemchinovka Federal Research Center in 2019-2020. The contamination of grain with fungi was determined by the mycological method and real-time PCR. The analysis of mycotoxins was carried out by ELISA. In oats, Alternaria (the grain infection was 15-90 %), Cochliobolus (1-33 %), Cladosporium (1-19 %), Epicoccum (0-11 %), and Fusarium (3-17 %) fungi prevailed in the grain mycobiota. The predominant Fusarium species were F. poae (its proportion among Fusarium fungi was 49-68 %) and F. langsethiae (29-28 %). The highest amounts of F. langsethiae DNA ((27.9-71.9) × 10-4 pg/ng) and T-2/HT-2 toxins (790-1230 µg/kg) were found in the grain of husked oat Yakov. Among the analysed naked oat lines, the amount of F. langsethiae DNA varied in the range of (1.2-42.7) × 10-4 pg/ng,and the content of T-2/HT-2 toxins was in the range of 5-229 µg/kg. Two oat breeding lines, 54h2476 and 66h2618, as well as a new variety, Azil (57h2396), can be characterized as highly resistant to infection with Fusarium fungi and contamination with mycotoxins compared to the control variety Vyatskiy.

[The effectiveness of molecular markers for the identification of Lr28, Lr35, and Lr47 genes in common wheat].

The effectiveness of molecular markers for the identification of leaf rust resistance genes Lr28, Lr35, Lr47 transferred to common wheat was assessed the using samplesof Triticum spp. and Aegilops spp. from Ae. speltoides. Markers Sr39F2/R3, BCD260F1/35R2 of gene Lr35 and PS10 of Lr47 gene were characterized by high efficiency and were revealed in a line of common wheat containing these genes, and samples of Ae. speltoides (their donor). Marker SCS421 of Lr28gene and markers Sr39#22r, Sr39#50s, BE500705 of Lr35/Sr39 genes turned out to be less specific. Marker SCS421 was amplified in the samples of the T. timopheevii species, and markers Sr39#22r, Sr39#50s--in the Ae. speltoides, Ae. tauschii, T. timopheevii, line KS90WRC010 (Lr41), the sort of common wheat In Memory of Maistrenko, obtained using synthetic hexaploid T. timopheevii x Ae. tauschii and introgressive lines obtained using Ae. speltoides. Marker BE500705, which indicates the absence of Lr35/Sr39 genes, was not revealed in lines TcLr35 and MqSr39, in Ae. speltoides, Ae. tauschii and T. boeoticum (kk-61034, 61038). Analysis of the nucleotide sequences of amplification products obtained with the markers SCS421 and Sr39#22r indicated their low homology with TcLr28 and TcLr35. Using molecular markers, we showed a different distribution of Lr28 (77%), Lr35 (100%) and Lr47 (15%) genes in 13 studied samples ofAe. speltoides. In introgressive lines derived from Ae. speltoides, contemporary Russian sorts of common wheat and triticale variants Lr28, Lr35, Lr47 genes were not revealed.